Physics ITT

eVitO · 06-28-2011, 06:43 PM

So, long story short, taking a physics class at a local CC and learning about friction, yada yada. Prof asked the class why racecars have wide tires, and I'm not a physics major so I was stumped with the rest of 'em.

So, why do racecars have wide tires? Considering friction is independent of surface area, it throws out any theories I have...

CollinsE90 · 06-28-2011, 06:49 PM

Because Race Car

TiAg335i · 06-28-2011, 06:51 PM

wider tires have better lateral traction and have better heat management properties than narrow tires

E90SoFlo · 06-28-2011, 06:51 PM

wider tires make stuff go faster. duh

eVitO · 06-28-2011, 06:59 PM

Quote:

Originally Posted by TiAg335i

wider tires have better lateral traction and have better heat management properties than narrow tires

'scoose my ignorance, but what IS lateral traction?

TimZ · 06-28-2011, 07:00 PM

Is friction really independent of surface area? The coefficient of friction is independent, but the overall magnitude of friction might be affected by the surface area in contact with the road and the weight of the car.
Hmm good question though, and good topic lol

Mr Tonka · 06-28-2011, 07:01 PM

lateral grip is how much grip the tire has when going around a turn. You might recognize the term Lateral G's from car mags. Tires have much to do with this figure.

ErvGotti · 06-28-2011, 07:03 PM

Quote:

Originally Posted by eVitO

'scoose my ignorance, but what IS lateral traction?

When your making a turn a wider tire will have more surface area contacting the road than a narrow tire.

SchlauCow · 06-28-2011, 07:03 PM

Well, considering this was a high school with ash-trays, I'd imagine your professor wanted you to ask a BMW forum for an insightful answer... or google.com.

eVitO · 06-28-2011, 07:06 PM

Quote:

Originally Posted by TimZ

Is friction really independent of surface area? The coefficient of friction is independent, but the overall magnitude of friction might be affected by the surface area in contact with the road and the weight of the car.
Hmm good question though, and good topic lol

That's what I thought... f=m*g*(mu) proved me wrong and I was like durr.

eVitO · 06-28-2011, 07:08 PM

Quote:

Originally Posted by SchlauCow

Well, considering this was a high school with ash-trays, I'd imagine your professor wanted you to ask a BMW forum for an insightful answer... or google.com.

It's extra credit, but considering google has more worthless answers than religion (sorry if I offended anyone), I thought I'd ask people who are even slightly interested in this topic as well.

eVitO · 06-28-2011, 07:09 PM

Quote:

Originally Posted by ErvGotti

When your making a turn a wider tire will have more surface area contacting the road than a narrow tire.

But again, surface area is independent of friction, so I still don't understand where this puts me at...

Mr Tonka · 06-28-2011, 07:14 PM

it's kind of a loaded question. There are so many things that go in to getting grip from a tire. Width is part of the equation but the most true answer would be: Because the sanctioning body for the racing series dictates what size tires they use; they are usually wide.

Non fancy physics answer:
Tires can only do 3 things for a car. Make it go forward, stop the car and turn the car. Tires have X quantity for maximum grip. So that tire can only administer that much grip for one of those tasks. If you ask it to make the car go forward while turning, X quantity of max grip is split up between those two tasks. ie, 40% for lateral grip with 60% forward grip may be needed just after the apex of a turn. So one way to make that 40% and 60% equal more grip is to widen the tire. Others would be stiffen or soften the sidewall or make the rubber compound softer. There is a limit to the benefits of width though.

SchlauCow · 06-28-2011, 07:23 PM

Quote:

Originally Posted by eVitO

It's extra credit, but considering google has more worthless answers than religion (sorry if I offended anyone), I thought I'd ask people who are even slightly interested in this topic as well.

I commend you on your troll avoidance skills

eVitO · 06-28-2011, 07:24 PM

Quote:

Originally Posted by SchlauCow

I commend you on your troll avoidance skills

I figured NO ONE would help me if they just got angry at me.

eVitO · 06-28-2011, 07:31 PM

Quote:

Originally Posted by MP0WER

it's kind of a loaded question. There are so many things that go in to getting grip from a tire. Width is part of the equation but the most true answer would be: Because the sanctioning body for the racing series dictates what size tires they use; they are usually wide.

Non fancy physics answer:
Tires can only do 3 things for a car. Make it go forward, stop the car and turn the car. Tires have X quantity for maximum grip. So that tire can only administer that much grip for one of those tasks. If you ask it to make the car go forward while turning, X quantity of max grip is split up between those two tasks. ie, 40% for lateral grip with 60% forward grip may be needed just after the apex of a turn. So one way to make that 40% and 60% equal more grip is to widen the tire. Others would be stiffen or soften the sidewall or make the rubber compound softer. There is a limit to the benefits of width though.

Anyway you can give me the fancy physics answer?

Blake · 06-28-2011, 07:39 PM

Quote:

Originally Posted by CollinsE90

Because Race Car

fuck you

E90SoFlo · 06-28-2011, 07:39 PM

math sucks.

Wide tires work better because they provide more surface area contact with pavement.

Naptime · 06-28-2011, 07:53 PM

Wider tires look cool.

CollinsE90 · 06-28-2011, 08:11 PM

Quote:

Originally Posted by Blake

fuck you

schoy · 06-28-2011, 08:41 PM

The simple answer lies with wear and materials strength, not friction. Race cars have softer tires and thus wear faster (given all the lateral Gs). Unless you want to be changing tires every lap, you use wider tires.

Google is your friend.

eVitO · 06-28-2011, 08:48 PM

Quote:

Originally Posted by schoy

The simple answer lies with wear and materials strength, not friction. Race cars have softer tires and thus wear faster (given all the lateral Gs). Unless you want to be changing tires every lap, you use wider tires.

Google is your friend.

And also your worst enemy...

Quote:

It's because real friction forces, unlike the ones they teach you about in physics class, do depend on contact area.

http://www.physicsforums.com/archive...p/t-56486.html

06-28-2011, 06:49 PM	#2
CollinsE90 Where my bitches 784 Rep 1,924 Posts Drives: Cadillac coupe deville Join Date: Mar 2009 Location: street corner checking profits iTrader: (0)	Because Race Car __________________
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06-28-2011, 06:51 PM	#3
TiAg335i Trance Life 333 Rep 4,706 Posts Drives: 2007 E92 335i Join Date: Jan 2007 Location: Long Island, NY iTrader: (4)	wider tires have better lateral traction and have better heat management properties than narrow tires __________________ Vanguard V2 Exhaust//Vishnu DCI//ACM Angel Eyes
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06-28-2011, 06:51 PM	#4
E90SoFlo Banned 217 Rep 2,669 Posts Drives: E90 335i Join Date: Jun 2011 Location: Naples, FL iTrader: (9)	wider tires make stuff go faster. duh
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06-28-2011, 07:00 PM	#6
TimZ Lieutenant 33 Rep 576 Posts Drives: X5M Join Date: May 2010 Location: NYC iTrader: (0)	Is friction really independent of surface area? The coefficient of friction is independent, but the overall magnitude of friction might be affected by the surface area in contact with the road and the weight of the car. Hmm good question though, and good topic lol
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06-28-2011, 07:01 PM	#7
Mr Tonka is probably out riding. 6061 Rep 2,292 Posts Drives: Something Italian Join Date: Feb 2009 Location: Sweatypeninsula iTrader: (0)	lateral grip is how much grip the tire has when going around a turn. You might recognize the term Lateral G's from car mags. Tires have much to do with this figure. __________________ "There is no greater tyranny than that which is perpetrated under the shield of the law and in the name of justice. -Charles de Secondat"
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06-28-2011, 07:03 PM	#9
SchlauCow ****** 145 Rep 337 Posts Drives: Honda M6 Join Date: Mar 2010 Location: Radiance iTrader: (4)	Well, considering this was a high school with ash-trays, I'd imagine your professor wanted you to ask a BMW forum for an insightful answer... or google.com. __________________ You will never be as complex as the strand of hair sitting on top of your head.
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06-28-2011, 07:14 PM	#13
Mr Tonka is probably out riding. 6061 Rep 2,292 Posts Drives: Something Italian Join Date: Feb 2009 Location: Sweatypeninsula iTrader: (0)	it's kind of a loaded question. There are so many things that go in to getting grip from a tire. Width is part of the equation but the most true answer would be: Because the sanctioning body for the racing series dictates what size tires they use; they are usually wide. Non fancy physics answer: Tires can only do 3 things for a car. Make it go forward, stop the car and turn the car. Tires have X quantity for maximum grip. So that tire can only administer that much grip for one of those tasks. If you ask it to make the car go forward while turning, X quantity of max grip is split up between those two tasks. ie, 40% for lateral grip with 60% forward grip may be needed just after the apex of a turn. So one way to make that 40% and 60% equal more grip is to widen the tire. Others would be stiffen or soften the sidewall or make the rubber compound softer. There is a limit to the benefits of width though. __________________ "There is no greater tyranny than that which is perpetrated under the shield of the law and in the name of justice. -Charles de Secondat"
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06-28-2011, 07:39 PM	#18
E90SoFlo Banned 217 Rep 2,669 Posts Drives: E90 335i Join Date: Jun 2011 Location: Naples, FL iTrader: (9)	math sucks. Wide tires work better because they provide more surface area contact with pavement.
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06-28-2011, 07:53 PM	#19
Naptime #Hashtag 10 Rep 245 Posts Drives: around in circles Join Date: Jan 2011 Location: South Texas iTrader: (1)	Wider tires look cool.
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06-28-2011, 08:41 PM	#21
schoy Major 997 Rep 1,003 Posts Drives: Melbourne Red E90 M3 Join Date: Apr 2010 Location: USA iTrader: (0)	The simple answer lies with wear and materials strength, not friction. Race cars have softer tires and thus wear faster (given all the lateral Gs). Unless you want to be changing tires every lap, you use wider tires. Google is your friend.
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